The importance of cell-mediated immunity (CMI) in the pathophysiology of animal models of uveitis has been demonstrated. However its significance in most human uveitides is unclear. This lack of clarity is due in part to the lack of resolution of two issues: (1) whether the CMI demonstrated to antigens derived from ocular tissues is an important etiologic mechanism in human uveitis or is merely secondary to tissue injury; (2) if cellular reactivity is of biologic significance in these diseases, which ocular tissue antigens are of importance in the production of uveitis. The rosette and lymphocyte stimulation assays have been demonstrated to be sensitive measures of some parameters of CMI. In some human disease states alterations in T-cell number and function have been observed, and are of diagnostic and prognostic significance. In patients with uveitis, parameters of non-specific CMI will be measured using these assays to determine whether alterations in the immune status exist in uveitis, and whether these alterations are of diagnostic and prognostic value. Many patients with chorioretinitis have damaged retinal pigment epithelium. An isotope release assay and a leukocyte migration inhibition assay will be used to determine whether these patients have cellular reactivity to antigens derived from retinal pigment epithelium, and whether changes in reactivity occur with alterations in disease status. A study of immunosuppression as a treatment modality in patients with severe uveitis is currently ongoing. The above assays will be used to monitor these patients' immunologic status to determine the importance of CMI in these diseases, and whether some parameters of CMI correlate with changes in disease status on therapy or prognosis. Delineation of CMI in patients with uveitis will increase our understanding of the pathophysiology of this group of diseases, and possibly be of diagnostic, prognostic, and therapeutic value.